"We can absolutely say he's running now," said Jim Moore, a Pacific University professor who studies Oregon politics. "There's no reason for him to write to people in Iowa, other than he's testing the waters."

In an email, Merkley spokeswoman Sara Hottman didn't reject the possibility of a presidential run, saying "the senator is focused on supporting his colleagues in the the 2018 races right now."

The Oregon politician has enjoyed increased attention this year, positioning himself as one of the Senate's most outspoken opponents of President Donald Trump. He was the lone sitting senator to endorse Bernie Sanders in last year's presidential campaign.

After Trump's election, he railed against the president's executive orders to prevent those from Muslim-majority countries from entering the U.S., and voted against many of his cabinet nominees.

Most notably, he delivered a 15-hour speech from the Senate floor in an attempt to stall the confirmation of Supreme Court Justice Neil Gorsuch.

That attempt ultimately failed, but the move threw him into the spotlight and boosted his name recognition.

Oregonian politicians rarely come within striking distance of the presidency. In 1968, former Oregon Gov. Mark Hatfield landed on Richard Nixon's short list for vice president, but the appointment went to Maryland Governor Spiro Agnew.

Does Merkley have a real shot at the White House? It depends, Moore said. He could capture the progressive Bernie Sanders base, if its momentum continues into the election. But if the election is about identity politics – if voters want a woman or a person of color in office – Merkley could struggle, Moore said.

Merkley doesn't yet have the name-recognition of progressive darlings like Elizabeth Warren, Moore said, but it's still early.

"He has as good a shot of anyone, which means I don't think he has a great shot right now," he said. "But that's where everybody starts. And this is a first step."

Despite the partisan politics he has displayed since Trump's election, Merkley paints a picture of harmony in his op-ed, insisting that from what he's seen from Oregon town halls, liberals and conservatives aren't that different, after all.

"Back in D.C., everyone breaks out into their tribes girded for battle, but at home in Oregon (and in Iowa, too, I imagine), people just want answers," he wrote. "They want a health care system that is easy to understand and there when they need it. They want a job that pays a decent, living wage. They want to go to college without mortgaging their future and a fair shot to make their mark, without having to jump through extra hoops because of their race, gender, or anything other than work ethic and talent."

"If we embrace the powerful forces that unite us, we can create an America that inspires hope and optimism again," he wrote.

Merkley drew on his blue-collar background – his dad worked as a millwright and a mechanic – and said he was looking forward to attending a Sept. 10 corn feed held by liberal advocacy group Iowa for the Progress. He will speak alongside South Bend, Ind. Mayor Pete Buttigieg and U.S. Rep. Dave Loebsack.

"Iowa has some big elections coming up in 2018, a chance to choose what kind of state it wants to be," Merkley wrote. "And because of Iowa's outsized role in national politics, its example matters."

If Iowa voters choose correctly, he hinted, America could overcome some of its most pressing problems.

"We can meet those challenges," he wrote, "in Iowa and across the nation, if we rise up together to take back our country in the name of We the People."

This story has been updated with additional comments from professor Jim Moore and a comment from Sen. Merkley's office.